RFR: 7174305: (ch) Channels.newReader doesn't throw IllegalBlockingModeException if channel is configured non-blocking [v2]

[Brian Burkhalter]

> Modify `sun.nio.cs.StreamDecoder::readBytes` to throw `IllegalBlockingModeException` if its channel is configured to be non-blocking.

Brian Burkhalter has updated the pull request incrementally with one additional commit since the last revision:

  7174305: Catch expected IllegalBlockingMode in test

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Changes:
  - all: https://git.openjdk.org/jdk/pull/12478/files
  - new: https://git.openjdk.org/jdk/pull/12478/files/651e5929..ab318551

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12478&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12478&range=00-01

  Stats: 7 lines in 1 file changed: 5 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/12478.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12478/head:pull/12478

PR: https://git.openjdk.org/jdk/pull/12478